Comment 2 for bug 667418

the line in /etc/nsswith.conf in question looks like:
    hosts: files dns mdns4

but pkg_prerm says:
    grep "hosts:\s*files dns mdns$"

This can be easily fixed by changing that to mdns4

However, this is prone to future problems. I'll see if a more sophisticated, position-independent "insert/remove" can be added, so it's workable for more than one libnss extensions.